Touge

A mountain pass is a navigable route through a mountain range or over a ridge. Since many of the world's mountain ranges have presented formidable barriers to travel, passes have played a key role in trade, war, and both human and animal migration throughout history. At lower elevations it may be called a hill pass. A mountain pass is typically formed between two volcanic peaks or created by erosion from water or wind.

Overview

Mountain passes make use of a gap, saddle, col or notch. A topographic saddle is analogous to the mathematical concept of a saddle surface, with a saddle point marking the highest point between two valleys and the lowest point along a ridge. On a topographic map, passes are characterized by contour lines with an hourglass shape, which indicates a low spot between two higher points. In the high mountains, a difference of between the summit and the mountain is defined as a mountain pass.

Passes are often found just above the source of a river, constituting a drainage divide. A pass may be very short, consisting of steep slopes to the top of the pass, or a valley many kilometers long, whose highest point might only be identifiable by surveying.

Roads have long been built through passes, as well as railways more recently. Some high and rugged passes may have tunnels bored underneath a nearby mountainside, as with the Eisenhower Tunnel bypassing Loveland Pass in the Rockies, to allow faster traffic flow throughout the year.

The top of a pass is frequently the only flat ground in the area, and is a high vantage point. In some cases this makes it a preferred site for buildings. If a national border follows a mountain range, a pass over the mountains is typically on the border, and there may be a border control or customs station, and possibly a military post as well. For instance Argentina and Chile share the world's third-longest international border, long. The border runs north–south along the Andes mountains, with a total of 42 mountain passes.

On a road over a pass, it is customary to have a small roadside sign giving the name of the pass and its elevation above mean sea level.

Apart from offering relatively easy travel between valleys, passes also provide a route between two mountain tops with a minimum of descent. As a result, it is common for tracks to meet at a pass; this often makes them convenient routes even when travelling between a summit and the valley floor. Passes traditionally were places for trade routes, communications, cultural exchange, military expeditions etc. A typical example is the Brenner pass in the Alps.

Some mountain passes above the tree line have problems with snow drift in the winter. This might be alleviated by building the road a few meters above the ground, which will make snow blow off the road.

Synonyms

There are many words for ''pass'' in the English-speaking world. In the United States, ''pass'' is very common in the West, the word ''gap'' is common in the southern Appalachians, ''notch'' in parts of New England, and ''saddle'' in northern Idaho.Map showing "saddle" names in Idaho
/ref> The term col, derived from Old French, is also used, particularly in Europe.

In the highest mountain range in the world, the Himalayas, passes are denoted by the suffix "La" in Tibetan, Ladhakhi, and several other regional languages. Examples are the Taglang La at 5,328 m (17,480 ft) on the Leh-Manali highway, or the Sia La at 5,589 m (18,337 ft) in the Eastern Karakoram range.

Scotland has the Gaelic term ''bealach'' (anglicised "balloch"), while Wales has the similar ''bwlch'' (both being insular Celtic languages). In the Lake District of north-west England, the term ''hause'' is often used, although the term ''pass'' is also common—one distinction is that a pass can refer to a route, as well as the highest part thereof, while a hause is simply that highest part, often flattened somewhat into a high-level plateau.

In Japan they are known as ''tōge'', which means "pass" in Japanese. The word can also refer to narrow, winding roads that can be found in and around mountains and geographically similar areas.

Around the world

There are thousands of named passes around the world, some of which are well-known, such as the Khyber Pass close to the present-day Afghanistan-Pakistan border on the ancient Silk Road, the Great St. Bernard Pass at in the Alps, the Chang La at , and the Khardung La at in Ladakh, India. The roads at Mana Pass at and Marsimik La at , on and near the China–India border respectively, appear to be world's two highest motorable passes. Khunjerab Pass between Pakistan and China at is also a high-altitude motorable mountain pass. One of the famous but non-motorable mountain passes is Thorong La at in Annapurna Conservation Area, Nepal.

Gallery

Stilfser Joch Ost.jpg, Stelvio Pass in the Alps (Italy)
Agua negra argentina.JPG, Agua Negra Pass between Argentina and Chile.
Bealach na Ba Pano.jpg, The Bealach na Bà linking Applecross in the Scottish North-west Highlands.
Dead Woman's Pass from above.jpg, Dead Woman's Pass on the Inca Trail to Machu Picchu in Peru
Ornak a14.jpg, Pass in Tatras (Ornak, Poland).
Zadielska tiesnava.jpg, Zádielska tiesňava Pass in Slovak Karst (Slovakia).
Way to Thorong La.JPG, Trail from Manang to Mustang via Thorong La pass, Nepal.
CrawfordNotchCenter.jpg, Crawford Notch in New Hampshire, U.S.

See also

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References

Notes

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Montane ecology
Oronyms
Slope landforms
Walking
Adventure travel
Tourist activities
Geography